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Rates of Reaction

Rates of Reaction. Mrs. Coyle. How fast does aging occur?. http://www.ging-strategie.de/Anti%20Aging%20Strategie.JPG. How fast does the candle burn?. http://images.usatoday.com/tech/_photos/2006/03/28/aprilfig1.jpg. Reaction Rate. The speed with which products form from the reactants.

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Rates of Reaction

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  1. Rates of Reaction Mrs. Coyle

  2. How fast does aging occur? http://www.ging-strategie.de/Anti%20Aging%20Strategie.JPG

  3. How fast does the candle burn? http://images.usatoday.com/tech/_photos/2006/03/28/aprilfig1.jpg

  4. Reaction Rate The speed with which products form from the reactants.

  5. Exo- and Endothermic Reactions Exothermic reaction: reaction gives off energy. reactants products + energy Endothermic reaction: reaction takes in energy. energy + reactants products

  6. Bonds and Energy When bonds are broken: energy is absorbed. (analogy: stretching a rubber band) When bonds are formed : energy is released. (analogy: releasing a stretched rubber band)

  7. Ex: Exothermic • H2 + Cl2 2 HCl + 183 kJ/mol

  8. Ex: Endothermic 2HgO + 181.7 kJ  2Hg + O2

  9. Net Energy Change DH= Potential Energy of Products -Potential Energy of Reactants DH <0 exothermic DH >0 endothermic

  10. Collision Theory of Reactions http://staff.um.edu.mt/jgri1/teaching/che2372/notes/10/10_19.gif

  11. Activation Energy • Minimum amount of kinetic energy the reactants must have in order to react. • The particles form an activated complex (transition state) that is an unstable arrangement of atoms that lasts a few moments. Then the products are formed.

  12. Analogy http://www.800mainstreet.com/7/0007-004-reac_rate2.htm

  13. Potential Energy vs Time (Exothermic) Heat of Reaction DH Time http://staff.um.edu.mt/jgri1/teaching/che2372/notes/10/theory.html

  14. Energy vs Time (Endothermic) Activation Energy Heat of Reaction DH

  15. Reaction Rates are affected by: • Concentration • Temperature • Catalyst • Surface Area (Particle Size) • Mixing (Stirring)

  16. Concentration Effect on Reaction Rates The more concentrated, the higher the reaction rate. Why? http://content.answers.com/main/content/wp/en/thumb/f/ff/525px-Molecular-collisions.jpg

  17. Temperature Effect on Reaction Rates The higher the temperature, the faster the rate. Why?

  18. Catalyst Effect on Reaction Rates A catalyst lowers the activation energy, thus the reaction proceeds faster.

  19. Particle Size (Surface Area) • The smaller the particle size the faster the rate.

  20. Inhibitors • Substances that negate the effect of the catalyst.

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